1. Field of the Invention
The present invention relates, in general, to devices and methods for maintaining air conditioning or refrigerant equipment, and in particular, to a method and system for removing liquid chlorinated fluorocarbon refrigerant from an air conditioning unit, cleaning the removed refrigerant, and replacing it back into the air conditioning unit.
2. Information Disclosure Statement
Air conditioning units which use chlorinated fluorocarbon (CFC) refrigerant often have to be periodically serviced, necessitating the removal from the air conditioning unit of the CFC refrigerant prior to repair, and the subsequent return to the air conditioning unit of the refrigerant following repair. CFC refrigerants, many of which are sold by DuPont under the well known trademark FREON, have various boiling points, depending on the particular type of CFC refrigerant, some typical types of CFC refrigerants are, for example, well known in industry as R-11, R-12, R-22, R-500, and R-502, with some types being more suited to certain applications than others due to their particular boiling point, and, consequently, their operating pressures and temperatures, when used in a refrigeration or air conditioning system. R-11 refrigerant is particularly difficult to remove from an air conditioning unit, since machines which employ R-11 typically operate under a sixteen inch vacuum and a nine pound head pressure within the air conditioning unit, and thus operate at much lower pressures than air conditioning units using other refrigerants, whose operating pressures range from ten to hundreds of pounds.
For many years, it was the practice in the industry to remove CFC refrigerant from an air conditioning unit simply by releasing it into the atmosphere. Recently, however, because of concerns for the environment and possible destruction of the protective ozone layer above the earth, it has become desirable, and in many cases mandated by law, to reclaim and recycle CFC refrigerant by removing it from an air conditioning unit, cleaning the refrigerant, and then replacing the cleaned refrigerant back into the air conditioning unit, preferably without allowing the escape of any CFC refrigerant into the atmosphere during this process.
Environmental concerns, though significant, are not the only factor in favor of recycling and reusing CFC refrigerant rather than releasing it into the atmosphere In recent years, the cost of CFC refrigerant has escalated drastically, having doubled or tripled in the past decade. For this reason, it is not only desirable to remove CFC refrigerant from an air conditioning unit prior to service, but to evacuate as much refrigerant vapor from the air conditioning unit after removal as is possible, substantially eliminating the release of any CFC vapor to the atmosphere when the air conditioning unit is opened for service. For example, a large 1200 ton air conditioning unit typically holds 2500 pounds of refrigerant. If even three percent of the refrigerant is not evacuated from the air conditioning unit prior to opening the unit, 75 pounds of refrigerant will be released into the atmosphere, an act which is expensive as well as being harmful to the environment. Therefore, it is desirable that the capability of refrigerant removal and replacement also be accompanied by the capability of evacuating the air conditioning unit to a vacuum following refrigerant removal, as well as the capability of self-evacuating the refrigerant recovery apparatus following refrigerant replacement, so that no significant amount of refrigerant is lost when the air conditioning unit and recovery apparatus are separated and subsequently opened to the atmosphere.
It is also highly desirable that any refrigerant recovery apparatus be portable. Air conditioning systems are typically located on the roof of a building, and any refrigerant recovery apparatus must be transported to the roof in order to be attached to the air conditioning unit. Some prior refrigerant recovery machines use water or air to cool the refrigerant as it is being removed from the air conditioning unit. Those refrigerant recovery machines which require a source of water for their operation are unusable atop those buildings that lack a water supply on the roof. Those refrigerant recovery machines which use air to cool the refrigerant as it is being removed may take several days to remove the refrigerant from an air conditioning unit since temperatures may be in excess of 100 degrees Fahrenheit on the roof, imposing a great cooling burden on what must necessarily be a small, portable apparatus. Other known methods of refrigerant recovery use refrigerant from the air conditioning unit itself, cooled by the air conditioning unit, to cool the refrigerant being removed. Obviously, such methods require that the air conditioning unit be operational to remove refrigerant therefrom, and are incapable of removing refrigerant from a poorly operating air conditioning unit, even though such an inoperative unit is the most likely candidate for refrigerant removal. Thus, it is highly desirable that a refrigerant recovery apparatus or method not require the use of a source of water, and that refrigerant recovery may proceed unassisted by the air conditioning unit from which the refrigerant is being removed. Also, the cooling ability of water or air-cooled refrigeration units is constrained, as neither can cool refrigerant below the temperature of the water or air employed as a heat transfer medium. An air-cooled unit is therefore unable to cool refrigerant below the ambient air temperature which, as mentioned above, may be 100 deqrees Fahrenheit or more at the site of the air conditioning unit. Similarly, a water cooled unit is unable to cool refrigerant below the temperature of its water source, which is usually either from a municipal water supply or a well-known water tower, with typical temperatures of sixty-five degrees and eighty degrees Fahrenheit, respectively. In any event, for obvious reasons, a water cooled unit is unable to cool refrigerant below the freezing point of water, approximately thirty-two degrees Fahrenheit.
A well known method for pressure testing air conditioning units is to pressurize the air conditioning unit with nitrogen and then examine the unit for leaks. An air conditioning unit cannot function if pressurized with nitrogen, so after the leaks have been located and repaired, the air conditioning unit has typically been purged to the atmosphere, releasing not only the nitrogen gas, but also refrigerant vapor. Also, the oil within the compressor of air conditioning units must be periodically changed or cleaned. Prior methods of removing the oil similarly involve pressurizing the air conditioning unit with nitrogen to force the oil out of the unit, or opening the air conditioning unit to the atmosphere. It would be highly desirable to eliminate both the use of nitrogen pressurization of the air conditioning unit to check leaks and remove oil as well as the need to open the air conditioning unit to the atmosphere to replace the oil therein, thus eliminating the subsequent release of refrigerant vapor when the nitrogen is purged from the machine or when the unit is opened to the atmosphere.
Unless a mechanism is also provided for cleaning, decontaminating, and recycling the removed refrigerant, however, replacement of the refrigerant back into the air conditioning unit would be unwise. Air conditioning units operate less efficiently if moisture is contained within their CFC refrigerant. It is therefore desirable that refrigerant moisture removal be a part of the refrigerant recycling operation.
It is also desirable for a refrigerant recovery apparatus to have the ability to wash the interior of the air conditioning unit prior to refrigerant replacement. If, for example, a motor bearing has burned out on the air conditioning unit, the interior passageways of the unit, as well as the refrigerant, will be contaminated. Were only the refrigerant to be decontaminated, and then replaced without cleaning the air conditioning unit as well, the refrigerant would then become contaminated again. A thorough treatment of the refrigerant recycling problem should address the cleaning of the air conditioning unit as well.
Some prior apparatus for refrigerant removal and processing require various couplings between the apparatus and the air conditioning unit being serviced to be moved from one point to another in order to reconfigure the apparatus for different modes of operation. This connection and disconnection of couplings provides the opportunity for CFC refrigerant release into the atmosphere, is therefore undesirable, and should preferably be minimized.
Finally, since R-11 refrigerant machines operate with refrigerant under a vacuum, over time, air will leak into such a system, and must be periodically purged, typically by the use of expensive purge pumps. It would be an added benefit if an otherwise idle refrigerant recovery system could be used to purge an air conditioning unit of air.
A preliminary patentability search in class 62, subclasses 292 and 474, produced the following patents, some of which may be relevant to the present invention: Sparano, U.S. Pat. No. 3,232,070, issued Feb. 1, 1966; Margulefsky et al., U.S. Pat. No. 4,554,792, issued Nov. 26, 1985; Scuderi, U.S. Pat. No. 4,766,733, issued Aug. 30, 1988; Manz et al., U.S. Pat. No. 4,805,416, issued Feb. 21, 1989; Manz et al., U.S. Pat. No. 4,809,520, issued Mar. 7, 1989; Lofland, U.S. Pat. No. 4,856,289, issued Aug. 15, 1989; Merritt, U.S. Pat. No. 4,903,499, issued Feb. 27, 1990; and, Proctor et al., U.S. Pat. No. 4,909,042, issued Mar. 20, 1990. A model DM-275 refrigerant recovery-recycling machine manufactured by Davco Manufacturing Co., Easton, Pa., as well as a model LV20 refrigerant recovery-recycling machine manufactured by National Refrigeration Products, Plymouth Meeting, Pa., are also known to perform retrieval of liquid CFC refrigerant from air conditioning units. Additionally, during the prosecution of the parent of this application, the Examiner cited Van Steenburgh, Jr., U.S. Pat. No. 4,967,570, issued Nov. 6, 1990, as an example of a refrigerant system liquid collection tank with means for cooling the refrigerant in order to further liquify refrigerant vapor in the tank and separate out non-condensable gas.
While each of the above patents disclose various apparatus for removing, cleaning, or replacing chlorinated fluorocarbon (CFC) refrigerant used in an air conditioning unit, none disclose or suggest the present invention. More specifically, none of the above patents disclose or suggest a method or system for removing liquid CFC refrigerant from an air conditioning unit, cooling the refrigerant in an evaporator which itself is cooled by liquid CFC refrigerant, storing the cooled refrigerant in a storage tank, and then pumping the refrigerant back into the air conditioning unit.
Sparano, U.S. Pat. No. 3,232,070, describes an apparatus for removing refrigerant from a disabled or inoperative air conditioning unit. Refrigerant is removed in vapor form from the air conditioning unit, compressed, and stored in a tank.
Margulefsky et al., U.S. Pat. No. 4,554,792, describes a filtering unit which may be inserted in-line with an air conditioning unit. The refrigerant passing therethrough is not cooled or removed, and is only filtered.
Scuderi, U.S. Pat. No. 4,766,733, describes a refrigerant reclamation and charging unit which uses a portion of the refrigerant being removed to cool the refrigerant itself. Unlike the present invention, the Scuderi patent has no separate cooling means with its own refrigerant, limiting the Scuderi patent to use with functional air conditioning units.
Manz et al., U.S. Pat. No. 4,805,416, and Manz et al., U.S. Pat. No. 4,809,520, describe a portable apparatus for removing refrigerant, said apparatus comprising, in series, an evaporator, a compressor, and a condenser, which empty the refrigerant into a tank. The Manz patents describe a very different structure of apparatus than the present invention, and do not utilize a separate coolant to cool the removed refrigerant.
Lofland, U.S. Pat. No. 4,856,289, describes a device for recovering and purifying refrigerant, in which the refrigerant is withdrawn from an air conditioning unit, then fully converted to vapor by superheating and distillation, then compressed, condensed, and then cooled by ambient air, in contrast to the present invention which uses cooling means, having a separate coolant, to cool the withdrawn refrigerant to speed up the removal process.
Merritt, U.S. Pat. No. 4,903,499, describes an apparatus which has an expansion valve that creates a pressure differential between the air conditioning unit and the refrigerant recovery system to urge the refrigerant to exit the air conditioning unit. A water cooled pressure vessel, having an axis in alignment with the gravity vector, is provided after the expansion valve to enhance the efficiency of a condenser following the pressure vessel.
Proctor et al., U.S. Pat. No. 4,909,042, describes an automobile air conditioner charging station which removes refrigerant from the air conditioner, compresses and condenses the refrigerant, and then stores the refrigerant in a holding tank. Sensing means attached to the tank determine the amount of refrigerant which has been removed, allowing a quantity of "make-up" refrigerant to be supplied upon recharging from a second auxiliary supply tank.